1. Biology SL Ms. Ragsdale

2.  Central Nervous System (CNS) – the control center of your brain  Receives all the impulses from your body and coordinates activity  Consists of the brain and spinal cord  Peripheral Nerves  Sensory and Motor System  Neurons – specialized cells that carry rapid electrical impulses

4.  Specialized cells that transmit information throughout the body very rapidly  3 Basic Parts of a Neuron  Dendrites – branched part of a neuron that are designed to create more surface area ▪ Used for connecting to other neurons or detect things about the environment  Cell Body – Main body of the cell containing the nucleus, mitochondria, ribosomes and other organelles  Axon – a long cable-like projection that carries the nerve impulses (action potential) away from the cell body ▪ Can be covered by a myelin sheath which is a protective layer of insulating fat

5.  Schwann cell – companion cells that wrap themselves around the axon many times over  What the myelin sheath is made up out of  Node of Ranvier – the gaps between myelin sheathes that help the impulse speed up  By interrupting the insulation at intervals, it allows the impulse to “jump” from node to node  Axon terminal – the place where one axon ends and forms a synapse with another neuron

7.  Nerve impulse can be passed from the axon of one neuron to the dendron of another at a synapse.  A nerve is a discrete bundle of several thousand neuron axons

8. 1. Sensory Neurons Have long axons and transmit nerve impulses from sensory receptors all over the body to the CNS 2. Motor Neurons Motor neurons also have long axons and transmit nerve impulses from the central nervous system to effectors (muscles and glands) all over the body 3. Interneurones (Connector or Relay neurons) Much smaller cells connect various neurons within the brain and spinal cord

10. Step I  Sensory Neurons are located around the body – skin, eyes, nose, tongue – that collect stimuli from Receptors  The stimuli are converted into energy in the form of a small impulse  The impulse is sent from the sensory nerves to the CNS using sensory neurons

11. Part II  The sensory neurons bring the impulse (message) to the relay neurons inside the CNS (brain and spinal cord)  The relay neurons move the message inside the brain and bring it to the correct spot  The CNS now sends out an impulse (message) to the motor neurons

12.  The motor neurons take the relayed message (impulse) to the effectors  Effectors are often muscles  Once the message is relayed, a response is produced

13.  Cross section of the vertebrae in the spinal column

15.  Synapse – a junction between two neurons  Synaptic cleft – the plasma membranes

17.  Resting Potential - the negative charge registered when the nerve is at rest and not conducting a nerve impulse  Action Potential - the positive electrochemical charge generated at the nerve impulse.  Depolarization - a change from the negative resting potential to the positive action potential  Repolarization - the change in the electrical potential from the positive action potential back to the negative resting potential